Hot water heater question

Why are y'all even worrying about this.
Turn it on and forget about it.

pianotuna wrote:
6 cycles per day to do not very much at all. The electric setting draws 1200 watts so that is 1.8 KWH of wasted energy.... But someone is paying the bill. If it is you, turn off and save your pennies.

OK. At 15¢/kwh (which is high) that would be 27¢/day.

Yes, you will be saving pennies.

For the real tight penny pinchers, with a lot of time on their hands, you can do your own study.

1. Leave the water heater on all day. Using gas or electric or both. Doesn't matter to me. Sit around all day and keep a record of how many minutes and seconds, total, that the water heater is active.

2. Turn it off after every use, and go about your normal routine, but don't wander away, because you have to count how many minutes and seconds, total, that the water heater is active. If you are the only one using water, it will be easier and you can wander away all you want.

It is simply a matter of totaling up the time and comparing.

Hi,

The ten gallon water heater on the electric setting cycles about every four hours and takes 15 minutes to reheat the water. That is with no water use. I've replicated those numbers when it is mid summer and when it is -37 c.

That is 6 cycles per day to do not very much at all. The electric setting draws 1200 watts so that is 1.8 KWH of wasted energy.

Assuming the water heater is turned off at 8 a.m. the water will still be quite usefully warm ten hours later.

If on campground power that is not metered, who cares? But someone is paying the bill. If it is you, turn off and save your pennies.

bpounds wrote:
Regarding the OP question, which included turning it on/off throughout the day as needed, there won't be a way to calculate the answer. Too many variables. How many times on/off? Outside temperature? Direction the wind is hitting the camper? Sun shining on the WH cover?

laknox wrote:
In my experience, straight propane recovery is much faster than straight AC recovery, so if you need quantities of hot water, propane is better. Best is to use both at the same time, if AC is available.

Lyle

That is by design
Propane burner supplies 8800 to 10,000/btu hr.
Electric is only 4777/btu hr. (1400W)

Electric recovery 6/gal hr.
Propane recovery 11.5-13.5/gal hr.
Combo recovery 18-20/gal hr.

bpounds wrote:
I'm in the 'who cares' camp.

Yeah, me too. Google searches reveal a slight advantage to turning it off, if you think it's worth saving a few pennies, which is about all you'll do.

pianotuna wrote:
Hi,

It is cheaper to turn it off.

I typically turn it on in the morning, do what I need to, and turn it off. There is enough residual heat so that by supper time the water is still hot enough to do the dishes.

You are definitely correct, if you don't turn it back on during the day. No brainer there.

Regarding the OP question, which included turning it on/off throughout the day as needed, there won't be a way to calculate the answer. Too many variables. How many times on/off? Outside temperature? Direction the wind is hitting the camper? Sun shining on the WH cover?

I'm in the 'who cares' camp. And I only use propane anyway. AC is shut off outside. Too much hassle to get to the switch and no good reason to do it. Don't want to waste generator power on heating water.

Hi,

It is cheaper to turn it off.

I typically turn it on in the morning, do what I need to, and turn it off. There is enough residual heat so that by supper time the water is still hot enough to do the dishes.

Sport45 wrote:

csamayfield55 wrote:
I don't have any exact numbers here but from someone who works around commercial AC and heating systems here is my thoughts. You can either take it or leave it.

It takes WAY more BTU's (British thermal unit's) to heat water from ambient temperature to say 120 deg. than it does to maintain that temperature for a period of time. The water heater may cycle 4 or 5 times a day for short periods but it is not nearly as much heat energy than letting it cool and then reheat even 2 times a day.

Same for your AC unit's. If you let your rig heat soak till it is too hot to bear inside then turn on your AC it will take much more energy to remove that heat than if you set your stat at a comfortable level and maintain that level.

Chris

Sounds good on the surface, but I ain't buying it.

The heat loss from the hot water tank is to the atmosphere through the insulation on the tank. Heat loss is a function of the temperature difference so the colder the water is the less btu's per hour are being lost. Keeping it hot 24 hrs/day means you are radiating the most heat to the atmosphere and that has to be replenished with propane or electricity. Allowing it to cool between uses radiates less heat and uses less energy in the long run. (Even if it seems like it's firing longer).

Well, I'm going to agree to disagree with you on this Sport45. I'm definitely buying what Chris is selling!

In my experience, straight propane recovery is much faster than straight AC recovery, so if you need quantities of hot water, propane is better. Best is to use both at the same time, if AC is available.

Lyle